Elevator landing door locks, which are commonly referred to as interlocks, are provided in elevator systems to lock hall doors against movement when the elevator car is not in position to receive loads. The interlock is a safety device that prevents access to an elevator shaft through the doors when the car is not present in the doorway. The interlock also prevents the elevator cab from moving before the door is closed and locked. Safety locks are required by numerous building safety codes.
Interlocks in common use with lifting devices are controlled by solenoids. While generally dependable, solenoids require a large coil to have sufficient power to engage and hold the locking mechanism in the ‘open’ position. The size of the coils that comprise these systems require that interlocks be bulky and unsightly when compared to most residential door locking mechanisms. These locks are commonly ‘normally closed’, such as by spring biasing, and rely on being energized to maintain an ‘open’ position. This design can prevent the hall door from being closed if the hall door is open and there is a power failure, since gravity moves the interlock into the ‘closed’ position, preventing the door from reclosing. There is a need for a device that will permit easy locking of the door if the operating device is not powered.